U.S. Pat. No. 5,324,800 discloses that certain substituted metallocenes when used in catalyst systems for producing olefin polymers produce higher activity than when one uses an unsubstituted metallocene such as bis(cyclopentadienyl)zirconium dichloride. The patent contains the broad statement that included among the possible substituents are various hydrocarbyl radicals having 1 to 20 carbon atoms. Arylalkyl radicals are recited as one example of such hydrocarbyl radicals. There is, however, only one arylalkyl substituted metallocene actually named, i.e. bis(beta-phenylpropyl cyclopentadienyl) zirconium dimethyl. See column 5, lines 23 and 24. Example 4 of the patent might conceivably have used bis(beta-phenylpropylcyclopentadienyl) zirconium dichloride; however, even that is just an assumption based on the fact that the symbols used in Example 4 were the same as those used in connection with the naming of the dimethyl metallocene in column 5, lines 23 and 24. From the nomenclature used in the patent it is assumed that in both of those metallocenes the substituted cyclopentadienyl group was 1-cyclopentadienyl-2-phenyl-2-methyl-ethane, that is to say that there were only two carbons separating tie cyclopentadienyl group and the phenyl group. Example 4 of that patent provides some evidence that that particular metallocene was slightly more than twice as active as the unsubstituted metallocene bis(cyclopentadienyl)zirconium dichloride.
The present inventors have since prepared the metallocenes bis(phenylmethylidene cyclopentadienyl) zirconium dichloride, bis(phenylethylidene cyclopentadienyl) zirconium dichloride, and bis (phenyl-n-propylidene cyclopentadienyl) zirconium dichloride, which could also be called bis(1-phenyl-3-cyclopentadienyl-n-propane) zirconium dichloride, and have used those metallocenes with an aluminoxane cocatalyst in the polymerization of olefins. It was observed that the activity increased as the length of the alkylidene group was increased. The first two named metallocenes gave activities that were much less than half of the activity of the later. It would therefor be logical to assume that the metallocene having the n-propylidene alkylene group connecting the phenyl and the cyclopentadienyl was more active than the metallocene of Example 4 of the above mentioned patent, said metallocene having only two carbons between the phenyl and the cyclopentadienyl rather than 3.
The applicants also prepared bis(phenyl-isopropylidene-cyclopentadienyl) zirconium dichloride, i.e. a metallocene in which the alkylene radical connecting the phenyl and the cyclopentadienyl was 1,1-dimethyl methylene. That metallocene was of very low activity as compared to that of even bis(phenylmethylidene cyclopentadienyl) zirconium dichloride and bis(phenylethylidene cyclopentadienyl) zirconium dichloride. The metallocene had an activity of only about 5.8 kg of polyethylene per hour which is even lower than that reported for the unsubstituted cyclopentadienyl metallocene bis(cyclopentadienyl) zirconium dichloride. See U.S. Pat. No. 5,780,659 which shows that under substantially the same polymerization conditions bis(cyclopentadienyl) zirconium dichloride had an activity of about 136 kg of polyethylene per hour.
The present invention is based in part upon the discovery that different aryl alkyl, aryl alkyl silyl, or aryl silyl substituted metallocenes produce unexpected effects when used with a cocatalyst in the polymerization of olefins.
Thus an object of the present invention is to provide certain metallocenes having unexpected properties. Another object is to provide processes for the polymerization of olefins using such metallocenes.